[PATCH] D152752: [MS] Fix passing aligned records by value in some cases

[Reid Kleckner via Phabricator via cfe-commits]

This revision was landed with ongoing or failed builds.
This revision was automatically updated to reflect the committed changes.
Closed by commit rG651e5ae62d29: [MS] Fix passing aligned records by value in some cases (authored by rnk).

Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D152752/new/

https://reviews.llvm.org/D152752

Files:
  clang/lib/CodeGen/TargetInfo.cpp
  clang/test/CodeGen/X86/x86_32-arguments-win32.c


Index: clang/test/CodeGen/X86/x86_32-arguments-win32.c
===================================================================
--- clang/test/CodeGen/X86/x86_32-arguments-win32.c
+++ clang/test/CodeGen/X86/x86_32-arguments-win32.c
@@ -1,4 +1,4 @@
-// RUN: %clang_cc1 -w -triple i386-pc-win32 -emit-llvm -o - %s | FileCheck %s
+// RUN: %clang_cc1 -fms-extensions -w -triple i386-pc-win32 -emit-llvm -o - %s | FileCheck %s
 
 // CHECK-LABEL: define dso_local i64 @f1_1()
 // CHECK-LABEL: define dso_local void @f1_2(i32 %a0.0, i32 %a0.1)
@@ -90,3 +90,41 @@
   gv128 = x + y + z + w + q;
 }
 // CHECK-LABEL: define dso_local x86_fastcallcc void @"\01 at fastcall_indirect_vec@84"(<4 x float> inreg noundef %x, <4 x float> inreg noundef %y, <4 x float> inreg noundef %z, ptr inreg noundef %0, i32 inreg noundef %edx, ptr noundef %1)
+
+struct __declspec(align(1)) Align1 { unsigned long long x; };
+struct __declspec(align(4)) Align4 { unsigned long long x; };
+struct __declspec(align(8)) Align8 { unsigned long long x; };
+void receive_align1(struct Align1 o);
+void receive_align4(struct Align4 o);
+void receive_align8(struct Align8 o);
+void pass_underaligned_record() {
+  struct Align1 a1;
+  receive_align1(a1);
+  struct Align4 a4;
+  receive_align4(a4);
+  struct Align8 a8;
+  receive_align8(a8);
+}
+// CHECK-LABEL: define dso_local void @pass_underaligned_record()
+// CHECK: call void @receive_align1(i64 {{[^,)]*}})
+// CHECK: call void @receive_align4(i64 {{[^,)]*}})
+// CHECK: call void @receive_align8(ptr {{[^,)]*}})
+
+struct FieldAlign1 { unsigned long long __declspec(align(1)) x; };
+struct FieldAlign4 { unsigned long long __declspec(align(4)) x; };
+struct FieldAlign8 { unsigned long long __declspec(align(8)) x; };
+void receive_falign1(struct FieldAlign1 o);
+void receive_falign4(struct FieldAlign4 o);
+void receive_falign8(struct FieldAlign8 o);
+void pass_underaligned_record_field() {
+  struct FieldAlign1 a1;
+  receive_falign1(a1);
+  struct FieldAlign4 a4;
+  receive_falign4(a4);
+  struct FieldAlign8 a8;
+  receive_falign8(a8);
+}
+// CHECK-LABEL: define dso_local void @pass_underaligned_record_field()
+// CHECK: call void @receive_falign1(i64 {{[^,)]*}})
+// CHECK: call void @receive_falign4(i64 {{[^,)]*}})
+// CHECK: call void @receive_falign8(ptr {{[^,)]*}})
Index: clang/lib/CodeGen/TargetInfo.cpp
===================================================================
--- clang/lib/CodeGen/TargetInfo.cpp
+++ clang/lib/CodeGen/TargetInfo.cpp
@@ -1893,9 +1893,21 @@
     llvm::IntegerType *PaddingType = NeedsPadding ? Int32 : nullptr;
 
     // Pass over-aligned aggregates on Windows indirectly. This behavior was
-    // added in MSVC 2015.
-    if (IsWin32StructABI && TI.isAlignRequired() && TI.Align > 32)
-      return getIndirectResult(Ty, /*ByVal=*/false, State);
+    // added in MSVC 2015. Use the required alignment from the record layout,
+    // since that may be less than the regular type alignment, and types with
+    // required alignment of less than 4 bytes are not passed indirectly.
+    if (IsWin32StructABI) {
+      unsigned AlignInBits = 0;
+      if (RT) {
+        const ASTRecordLayout &Layout =
+          getContext().getASTRecordLayout(RT->getDecl());
+        AlignInBits = getContext().toBits(Layout.getRequiredAlignment());
+      } else if (TI.isAlignRequired()) {
+        AlignInBits = TI.Align;
+      }
+      if (AlignInBits > 32)
+        return getIndirectResult(Ty, /*ByVal=*/false, State);
+    }
 
     // Expand small (<= 128-bit) record types when we know that the stack layout
     // of those arguments will match the struct. This is important because the


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